US3950748A - Method of and apparatus for stabilizing the display rate of permanent echoes in a radar system - Google Patents

Method of and apparatus for stabilizing the display rate of permanent echoes in a radar system Download PDF

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Publication number
US3950748A
US3950748A US05/480,145 US48014574A US3950748A US 3950748 A US3950748 A US 3950748A US 48014574 A US48014574 A US 48014574A US 3950748 A US3950748 A US 3950748A
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threshold
input signal
output signal
comparison
basic threshold
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Francis Busy
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Thomson CSF Visualisation et Traitement des Informations T V T
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/50—Systems of measurement based on relative movement of target
    • G01S13/52—Discriminating between fixed and moving objects or between objects moving at different speeds
    • G01S13/538—Discriminating between fixed and moving objects or between objects moving at different speeds eliminating objects that have not moved between successive antenna scans, e.g. area MTi

Definitions

  • My present invention relates to the determination of the optimum elimination threshold in a radar system for suppressing permanent echoes, applicable inter alia to multi-beam radar systems.
  • MTI moving-target indicators
  • An Area MTI eliminates permanent echoes in one area at a time and will be further described here since the system according to the invention is based on the same principle.
  • a discussion of an Area MTI can be found in Barton (Prentice Hall Series 1964) Radar System Analysis, page 224, or in Merrill Skolnik (Mc Graw Hill Book Co 1970) Radar Handbook, pages 17-54 and 17-55.
  • the radar area to be processed is divided into elementary compartments which receive a certain video-frequency energy at each revolution of the antenna. Upon each revolution, this energy is compared with a threshold which has been set to allow for the average energy received from a surveyed zone during the preceding antenna revolutions.
  • the threshold value S c (i- 1), set at the (i- 1)th antenna revolution, and compared with the energy received at the i th revolution is automatically adjusted for each zone thus swept by the antenna beam.
  • FIG. 1 shows the conventional method of setting the threshold used to determine the presence or absence of an echo from the target.
  • the variation in the threshold S c (i) is given in dependence on the antenna revolutions i, and the drawing shows the level CL corresponding to the noise amplitude in the swept zone and the energy corresponding to the undesired signals or clutter.
  • the desired signal corresponds to the instantaneous increase in average energy when a moving target travels through the compartment.
  • the threshold value is increased by a value M whenever an input signal occurring in the swept zone has an amplitude greater than the previously-set threshold, in which case an echo indication is transmitted to the radar receiver for display in the usual manner.
  • the threshold value is reduced by a value N if no input signal is present or if a signal is present and its amplitude is less than the previously-set threshold.
  • the values of M and N used to update the basic threshold S c are integers and different from one another, the increment M being made greater than the decrement N.
  • S c (i-1) is the threshold set before the last-mentioned antenna revolution but used as a comparison value for the energy received at the following or i th revolution
  • S c (i) is the threshold value obtained and therefore calculated after comparing the voltage Vi with the threshold S c (i-1)
  • Vi >S c (i-1) i.e. if there is an echo
  • variable threshold S c (i) is held close to the clutter level CL.
  • the residual clutter rate tx can be shown to be: ##EQU1##
  • the residual clutter rate is important, since it can be used for more accurately determining the modifications to be made to the set threshold in order to ensure optimum elimination of permanent echoes under various practical conditions.
  • the threshold value automatically follows slow fluctuations in the amplitude of the received signal, since the value of the threshold is periodically set at less than the signal amplitude CL due to permanent echoes. In accordance with formula (1), this comparison gives rise to a non-zero residual rate.
  • the object of the invention is to obtain a low residual clutter rate so as to improve the elimination of permanent echoes.
  • any change of the supplemental parameter K during a sweep of a surveyed zone is utilized in the next-following sweep of the same zone; thus, an echo is registered on the radar display whenever the input signal Vi in the current sweep i exceeds the algebraic sum of S c (i-1) and K(i-1).
  • the described technique can be extended to a multi-beam radar system, either by applying the given result to each beam or by first defining a threshold from a mixture of video signals from all the beams in question, or from groups of beams, and suubsequently modifying the threshold for each beam or group of beams.
  • FIG. 1 is a graph pertaining to the prior art as discussed above;
  • FIG. 2 shows a threshold-setting device in a conventional system for eliminating permanent echoes in one area of exploration at a time
  • FIG. 3 shows a device for setting the optimum elimination threshold according to the invention
  • FIG. 4 is a curve showing the position of the threshold in my improved system
  • FIG. 5 shows the echo pulses detected
  • FIG. 6 shows a device for determining the optimum elimination threshold in a multi-beam radar system, according to my invention
  • FIG. 7 shows a modification of the system of FIG. 6.
  • the determination of an optimum threshold for improved elimination of permanent echoes in a single beam or multi-beam radar system is dependent on a knowledge of the residual clutter rate when the radar system operates under normal conditions. I shall therefore first describe a prior-art Area MTI, since it is used in obtaining the optimum threshold according to the invention.
  • FIG. 2 shows an Area MTI for setting a reference threshold as defined in conjunction FIG. 1.
  • the video signals delivered by the associated radar system appear at 1 and are applied to a comparator 4 whose other input receives a variable threshold usually elaborated during the previous revolution of the antenna, i.e. S c (i-1).
  • a signal M is added to the threshold S c (i-1) delivered by a storage circuit 13 to an adder circuit 41 which then feeds a new threshold value to the storage circuit 13 via an OR circuit 43. If there is no echo, a similar process occurs in which a subtractor circuit 42 subtracts the signal N from the previously-defined threshold value S c (i-1). A new threshold S c (i) is then stored in circuit 13 via the OR circuit 43.
  • FIG. 3 shows a system according to my invention for setting the threshold in dependence on the residual clutter rate in a radar beam.
  • the residual clutter is compared with two limiting values serving as a standard of compression, namely the minimum rate (Tmin) and the maximum rate (Tmax), chosen in accordance with the desired residual rate, in accordance with the particular application.
  • a count is made of the number of video signals or input 1 exceeding above an adjustable but fixed reference threshold Sf applied to a comparator 3.
  • Threshold Sf can be of the kind used for automatically obtaining a given rate of false alarms.
  • the number of signals is registered in a counter 7, e.g. after being divided by 1000 in step down circuit 6 in order to obtain the proportion per thousand.
  • a count is also made of the number of video signals applied to input 1 and having an amplitude greater than the previously-defined modified threshold S c (i-1) + K(i-1), this number being registered in a second counter 8.
  • a divider circuit 9 establishes the ratio B/A between the data registered in counters 7 and 8, respectively, and the result TR ("residual rate") is compared with the limits value Tmin and Tmax in comparators 10 and 11, respectively.
  • rate T R lies between the minimum and maximum values
  • the calculation of the coefficient K is not modified by the control circuit 7-11. If, on the other hand, the comparison between the signals applied to comparator 10 shows that the value T R from divider 9 is less than the minimum rate, this means that the elimination has been excessive, i.e. that the coefficient K(i-1) added to the threshold S c (i-1) for the preceding revolution was too large and must be reduced. Conversely, if the comparison in circuit 11 indicates that rate T R is greater than the maximum rate, the elimination rate was insufficient and coefficient K(i-1) was too small and must be increased. Consequently, a control circuit 14 for calculating modified coefficient has inputs connected to circuit 9 via comparators 10 and 11 respectively.
  • the resulting new coefficient K(i) is stored in a circuit 15 which previously supplied the coefficient K(i-1), and is thence conveyed to an adder 16 which receives the threshold S c (i-1) stored in circuit 13.
  • Circuit 16 supplies the new optimum threshold, e.g. the parameter S c (i)+ K(i) for the i th antenna revolution, which is applied to one input of a comparison circuit 17 whose other input receives the video signals Vi appearing at the input 1 of the processing device.
  • the threshold S c (i) is again obtained, in the manner described in conjunction with FIG. 2 under the control of the comparison circuit 4 which receives the video signal Vi from the beam in question appearing at input 1 and also receives the value of the threshold S c (i-1) set during the preceding antenna revolution. This value is supplied by the store 13, which register the new threshold S c (i), working into counter 8.
  • Comparator 17 passes video signals having an amplitude greater than the new threshold in accordance with the inequality Vi > S c (i-1) + K
  • FIG. 4 illustrates the operation of the system of FIG. 3 by a curve C similar to the curve of FIG. 1, showing in dotted lines the calculated value K to the threshold S c , indicated in full lines, as well as the fixed incremental values M and N serving to update the basic threshold.
  • the clutter level is again shown by a line CL, the ordinate being used for the signal amplitude Vi and the abscissa being used for the antenna revolutions i.
  • FIG. 5 shows the video output signals and a useful signal (marked U) which exceeds the undesired-signal or clutter level.
  • the first echo pulses I1 to I4 appear during the time taken to establish the threshold.
  • the residual rate was calculated once for each antenna revolution.
  • This method gives a certain definition for radar detection.
  • the calculation can be made a number j of times per revolution, thus improving the definition of detection by dividing the radar coverage into j sectors (in azimuth) or rings (in range). Inside these zones, the thresholds or coefficients are determined according to the invention in the manner described. The amounts added or subtracted will be different from those previously mentioned.
  • FIG. 6 shows a system of this kind, where each beam f1, f2, . . . fn for producing signals V 1i , V 2i , . . . V ni is processed as described with reference to FIG. 3. If this method is used, however, the beam-processing circuits have to be multiplied by the number of beams.
  • FIG. 7 shows a modified system, designed to avoid this duplication of circuitry, wherein a base threshold is obtained from a mixture of video signals from all the beams, the threshold subsequently being modified for one beam at a time, depending on the clutter level for each beam.
  • a mixer 23 having a number of inputs for incoming beams f1 to fn receives the video signals therefore and delivers a composite signal which includes the individual signals, the composite signal being applied to one input of a first comparator 24 whose other input receives a reference signal representing a threshold SL c (i-1) set during the preceding reference period, i.e. the preceding antenna revolution or the sweep of the sector previously covered.
  • the comparison circuit 24 is connected to a circuit 25 for determining the threshold SL c (i) in the previously described manner, threshold generator 25 receiving signals M and N for increasing or decreasing the preceding threshold as required.
  • Circuit 25 is connected to a storage circuit 26 which registers the calculated threshold SL c (i) and supplies the threshold previously determined by the same method.
  • Threshold SL c (i-1) is used as a base for determining the modified threshold for stabilizing at an optimum value the display rate of permanent echoes in each beam.
  • the advantage of this base threshold is that it takes into consideration the video contents of each beam, so that it more closely follows the maximum clutter level in the beam in question.
  • each circuit for processing the video signals of a beam comprises a second comparator 27 to 27n receiving the energy collected in a beam and also receiving the previously-calculated threshold in the manner described with reference to FIG. 3.
  • the preceding threshold is equal to SL c1 (i-1) + K 1 (i-1) . . . SL cn (i-1) + K n (i-1) and is supplied by a circuit 31 to 31n connected to the store 26.
  • Each processor also comprises a computer 28 to 28n for determining the residual clutter rate, similar to the circuit arrangement described in connection with FIG. 3 for the case where the signals of a mono-beam radar system are processed, the computer receiving a threshold signal Sf 1 to Sf n .
  • the computer also receives signals corresponding to Tmax and Tmin respectively, i.e. to the maximum and minimum residual clutter. Depending on the individual case, the computer emits a signal T R at an output 280 or 281 indicating that the calculated residual clutter is either greater than the maximum or less than the minimum rate.
  • the emitted output signal is applied to a calculator 29 to 29n which, by the previously-defined process, determines the coefficient K 1 (i) . . . K n (i) whose value is added to the previously-defined threshold.
  • Coefficient K 1 to K n is stored in a circuit 30 to 30n and supplied to a circuit 31 to 31n at the next antenna revolution.
  • coefficient K 1 (i) is equal to the previously elaborated coefficient K 1 (i-1) augmented by a value p or diminished by a value q, depending on whether the calculated residual rate in circuit 28 is greater than the maximum or less than the minimum rate for displayed false alarms.
  • the value of p can be made dependent on the deviation between T R and the maximum rate, and q can be made dependent on the deviation between T R and the minimum rate.
  • Algebraic summing circuits 16, 31 . . . 31n may also operate as subtractors rather than adders, the modified threshold of inequality (2) then assuming the value S c (i-1) - K(i-1).

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  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Radar Systems Or Details Thereof (AREA)
US05/480,145 1973-06-19 1974-06-17 Method of and apparatus for stabilizing the display rate of permanent echoes in a radar system Expired - Lifetime US3950748A (en)

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FR7322308A FR2234571B1 (nl) 1973-06-19 1973-06-19

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Cited By (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4053885A (en) * 1975-04-03 1977-10-11 Nippon Electric Company, Ltd. Moving target indication radar
US4054872A (en) * 1975-08-08 1977-10-18 Siemens Aktiengesellschaft Pulse doppler radar receiver having a moving curve transit time filter
US4104633A (en) * 1977-04-18 1978-08-01 International Telephone And Telegraph Corporation Extended target-log CFAR processor
US7336219B1 (en) 2005-12-30 2008-02-26 Valeo Raytheon Systems, Inc. System and method for generating a radar detection threshold
US7379018B1 (en) * 2005-12-30 2008-05-27 Valeo Raytheon Systems, Inc. System and method for verifying a radar detection
US7683827B2 (en) 2004-12-15 2010-03-23 Valeo Radar Systems, Inc. System and method for reducing the effect of a radar interference signal
US20100238066A1 (en) * 2005-12-30 2010-09-23 Valeo Raytheon Systems, Inc. Method and system for generating a target alert
US20130328616A1 (en) * 2012-06-06 2013-12-12 Ford Global Technologies, Llc Proximity switch and method of adjusting sensitivity therefor
US9287864B2 (en) 2012-04-11 2016-03-15 Ford Global Technologies, Llc Proximity switch assembly and calibration method therefor
US9311204B2 (en) 2013-03-13 2016-04-12 Ford Global Technologies, Llc Proximity interface development system having replicator and method
US9447613B2 (en) 2012-09-11 2016-09-20 Ford Global Technologies, Llc Proximity switch based door latch release
US9520875B2 (en) 2012-04-11 2016-12-13 Ford Global Technologies, Llc Pliable proximity switch assembly and activation method
US9531379B2 (en) 2012-04-11 2016-12-27 Ford Global Technologies, Llc Proximity switch assembly having groove between adjacent proximity sensors
US9548733B2 (en) 2015-05-20 2017-01-17 Ford Global Technologies, Llc Proximity sensor assembly having interleaved electrode configuration
US9559688B2 (en) 2012-04-11 2017-01-31 Ford Global Technologies, Llc Proximity switch assembly having pliable surface and depression
US9568527B2 (en) 2012-04-11 2017-02-14 Ford Global Technologies, Llc Proximity switch assembly and activation method having virtual button mode
US9654103B2 (en) 2015-03-18 2017-05-16 Ford Global Technologies, Llc Proximity switch assembly having haptic feedback and method
US9660644B2 (en) 2012-04-11 2017-05-23 Ford Global Technologies, Llc Proximity switch assembly and activation method
US9831870B2 (en) 2012-04-11 2017-11-28 Ford Global Technologies, Llc Proximity switch assembly and method of tuning same
US9944237B2 (en) 2012-04-11 2018-04-17 Ford Global Technologies, Llc Proximity switch assembly with signal drift rejection and method
US10038443B2 (en) 2014-10-20 2018-07-31 Ford Global Technologies, Llc Directional proximity switch assembly
US10112556B2 (en) 2011-11-03 2018-10-30 Ford Global Technologies, Llc Proximity switch having wrong touch adaptive learning and method
CN116338647A (zh) * 2021-12-23 2023-06-27 深圳市速腾聚创科技有限公司 雷达系统、回波信号处理方法、装置及电子设备

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2535066B1 (fr) * 1982-10-22 1985-09-13 Thomson Csf Dispositif de determination du seuil d'elimination d'echos fixes, notamment pour recepteurs radar

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US3380018A (en) * 1967-03-20 1968-04-23 Navy Usa Digital density threshold for sonar
US3430235A (en) * 1964-05-01 1969-02-25 Avco Corp Automatic signal discriminator and threshold adjustment circuit for range-gated radar detection systems
US3505637A (en) * 1964-03-10 1970-04-07 Us Navy Digital overflow threshold for sonar
US3582872A (en) * 1964-06-29 1971-06-01 Us Navy Threshold control for sonar
US3761922A (en) * 1971-10-12 1973-09-25 Hughes Aircraft Co Digital mean level detector
US3778822A (en) * 1972-04-27 1973-12-11 Gen Electric Sum-rank normalized detection apparatus
US3778825A (en) * 1972-04-10 1973-12-11 Gen Electric Adaptive quantizing and integrating detector for pulse-echo systems

Patent Citations (7)

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Publication number Priority date Publication date Assignee Title
US3505637A (en) * 1964-03-10 1970-04-07 Us Navy Digital overflow threshold for sonar
US3430235A (en) * 1964-05-01 1969-02-25 Avco Corp Automatic signal discriminator and threshold adjustment circuit for range-gated radar detection systems
US3582872A (en) * 1964-06-29 1971-06-01 Us Navy Threshold control for sonar
US3380018A (en) * 1967-03-20 1968-04-23 Navy Usa Digital density threshold for sonar
US3761922A (en) * 1971-10-12 1973-09-25 Hughes Aircraft Co Digital mean level detector
US3778825A (en) * 1972-04-10 1973-12-11 Gen Electric Adaptive quantizing and integrating detector for pulse-echo systems
US3778822A (en) * 1972-04-27 1973-12-11 Gen Electric Sum-rank normalized detection apparatus

Cited By (25)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4053885A (en) * 1975-04-03 1977-10-11 Nippon Electric Company, Ltd. Moving target indication radar
US4054872A (en) * 1975-08-08 1977-10-18 Siemens Aktiengesellschaft Pulse doppler radar receiver having a moving curve transit time filter
US4104633A (en) * 1977-04-18 1978-08-01 International Telephone And Telegraph Corporation Extended target-log CFAR processor
US7683827B2 (en) 2004-12-15 2010-03-23 Valeo Radar Systems, Inc. System and method for reducing the effect of a radar interference signal
US7336219B1 (en) 2005-12-30 2008-02-26 Valeo Raytheon Systems, Inc. System and method for generating a radar detection threshold
US7379018B1 (en) * 2005-12-30 2008-05-27 Valeo Raytheon Systems, Inc. System and method for verifying a radar detection
US20100238066A1 (en) * 2005-12-30 2010-09-23 Valeo Raytheon Systems, Inc. Method and system for generating a target alert
US10501027B2 (en) 2011-11-03 2019-12-10 Ford Global Technologies, Llc Proximity switch having wrong touch adaptive learning and method
US10112556B2 (en) 2011-11-03 2018-10-30 Ford Global Technologies, Llc Proximity switch having wrong touch adaptive learning and method
US9520875B2 (en) 2012-04-11 2016-12-13 Ford Global Technologies, Llc Pliable proximity switch assembly and activation method
US9568527B2 (en) 2012-04-11 2017-02-14 Ford Global Technologies, Llc Proximity switch assembly and activation method having virtual button mode
US9287864B2 (en) 2012-04-11 2016-03-15 Ford Global Technologies, Llc Proximity switch assembly and calibration method therefor
US9944237B2 (en) 2012-04-11 2018-04-17 Ford Global Technologies, Llc Proximity switch assembly with signal drift rejection and method
US9531379B2 (en) 2012-04-11 2016-12-27 Ford Global Technologies, Llc Proximity switch assembly having groove between adjacent proximity sensors
US9831870B2 (en) 2012-04-11 2017-11-28 Ford Global Technologies, Llc Proximity switch assembly and method of tuning same
US9559688B2 (en) 2012-04-11 2017-01-31 Ford Global Technologies, Llc Proximity switch assembly having pliable surface and depression
US9660644B2 (en) 2012-04-11 2017-05-23 Ford Global Technologies, Llc Proximity switch assembly and activation method
US9337832B2 (en) * 2012-06-06 2016-05-10 Ford Global Technologies, Llc Proximity switch and method of adjusting sensitivity therefor
US20130328616A1 (en) * 2012-06-06 2013-12-12 Ford Global Technologies, Llc Proximity switch and method of adjusting sensitivity therefor
US9447613B2 (en) 2012-09-11 2016-09-20 Ford Global Technologies, Llc Proximity switch based door latch release
US9311204B2 (en) 2013-03-13 2016-04-12 Ford Global Technologies, Llc Proximity interface development system having replicator and method
US10038443B2 (en) 2014-10-20 2018-07-31 Ford Global Technologies, Llc Directional proximity switch assembly
US9654103B2 (en) 2015-03-18 2017-05-16 Ford Global Technologies, Llc Proximity switch assembly having haptic feedback and method
US9548733B2 (en) 2015-05-20 2017-01-17 Ford Global Technologies, Llc Proximity sensor assembly having interleaved electrode configuration
CN116338647A (zh) * 2021-12-23 2023-06-27 深圳市速腾聚创科技有限公司 雷达系统、回波信号处理方法、装置及电子设备

Also Published As

Publication number Publication date
NL7408119A (nl) 1974-12-23
BE816590A (fr) 1974-12-19
GB1479665A (en) 1977-07-13
DE2429024B2 (de) 1976-01-15
FR2234571B1 (nl) 1976-04-30
FR2234571A1 (nl) 1975-01-17
NL184978C (nl) 1989-12-18
IT1015118B (it) 1977-05-10
NL184978B (nl) 1989-07-17
DE2429024A1 (de) 1975-01-02

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